Large commercial passenger-carrying aircraft have galleys for preparing and serving food and beverages during the flight. These galleys are equipped with ovens, beverage makers, trash compactors, and various other kitchen type appliances used in the preparation and serving of the food and beverages. The galley also includes carts or trolleys that can be rolled down the aisles of the aircraft to serve meals and beverages to the passengers. As with all aircraft systems, these galleys and the equipment used therein must adhere to guidelines for weight and space, which are both premiums on an aircraft. As part of the food and beverage service, perishables are stored and then served on the flight. Perishables create a problem for aircraft operators because traditional refrigeration systems are too heavy and take up too much space to function in the aircraft galley. Thus, the aircraft manufactures must design a way to keep the perishables fresh during flight without refrigerators on the aircraft.
To this end, most commercial aircraft employ one of two types of systems for keeping perishable food stuffs and non-perishable drinks at desired temperatures from loading to service on the flight. The first method utilizes vapor cycle based air chillers that utilize conventional refrigerant gas compression and expansion technology to generate a secondary recirculated chilled air loop. The chilled air is generally supplied and returned via a thermally insulated air ducting to and from a suitable storage structure, such as the galley. The air chiller may be located on or in the galley or mounted in part of the aircraft airframe.
The second method utilizes the same conventional refrigerant gas compression and expansion technology, but the cooling medium is a chilled liquid rather than a gas. This chilled liquid is pumped in a closed loop to and from a suitable storage structure, such as a galley. The chilled liquid in some cases are configured as a large centralized system for the whole aircraft. In other cases, the chilled liquid can be circulated at each separate aircraft galley structure to establish a local area chilling loop, or be based on each individual galley as a standalone system. At the galley, the liquid is passed via a control valve and an electronic control system to a heat exchanger, where an electric axial (or other) fan blows or sucks air through its matrix around enclosed areas of the storage structure that requires chilling, for example: a galley cart bay or compartment. The heat exchanger fan and its control system (though not necessarily all) are grouped together to form a chilled air recirculation unit that may be fitted in the galley or remotely spaced from it.
One drawback of these various chiller systems is that they still take up a large percentage of available space in the galley, which is at a premium in an aircraft for obvious reasons. Further, the chillers tend to be very heavy, which is also a drawback to their use on aircraft. There are also issues with condensation collection and removal, and the need for improvements in heat transfer efficiency. Further, air control flaps are necessary to reduce the loss of chilled air, which makes the system more inefficient. Accordingly, it would be beneficial to have a chiller system that takes up less space and reflects a reduction in weight over conventional chiller systems currently in use, while providing for condensation collection and improved heat transfer efficiency.